Foil structures for use in a capacitor with an anode foil and a cathode foil stacked together

ABSTRACT

In one aspect, a method of interconnecting two or more foils of a capacitor, the method comprising connecting together one or more anode connection members of one or more anode foils and one or more cathode connection members of one or more cathode foils and electrically isolating the one or more anode foils from the one or more cathode foils.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a division of U.S. application Ser. No. 10/299,234,filed on Nov. 19, 2002, now U.S. Pat. No. 6,709,946, which is a divisionof U.S. application Ser. No. 09/706,519, filed on Nov. 3, 2000, nowissued as U.S. Pat. No. 6,509,588, the specifications of which arehereby incorporated by reference.

This application is related to application Ser. No. 09/706,447, filed onNov. 3, 2000, now issued as U.S. Pat. No. 6,699,267, the specificationof which is hereby incorporated by reference.

FIELD OF THE INVENTION

The present invention concerns implantable medical devices, such asdefibrillators and cardioverters, particularly structures and methodsfor capacitors in such devices.

BACKGROUND

Capacitors have undergone substantial improvement over the years.Smaller capacitors are in demand for various applications. One suchapplication is for biomedical implants. For example, defibrillators andpacemakers use capacitors for pulse delivery.

The defibrillator or cardioverter includes a set of electrical leads,which extend from a sealed housing into the walls of a heart afterimplantation. Within the housing are a battery for supplying power,monitoring circuitry for detecting abnormal heart rhythms, and acapacitor for delivering bursts of electric current through the leads tothe heart.

The capacitor can take the form of a flat aluminum electrolyticcapacitor. Flat capacitors include a stack of flat capacitor elementsmounted within a capacitor case. Each flat capacitor element includesone or more separators between two sheets of aluminum foil. One of thealuminum foils serves as a cathode (negative) foil, and the other servesas an anode (positive) foil. The capacitor elements each have anindividual capacitance (or energy-storage capacity) proportional to thesurface area of the foil.

One drawback in manufacturing such capacitors is that each of the anodesand each of the cathodes must be connected together. For instance, allthe anodes are crimped or welded together and attached to a feedthroughterminal for connection to circuitry outside the capacitor case. Anotherprocess is also done for the cathode foils in the capacitor stack.Errors during the manufacturing steps may cause defects in the capacitoror decrease the reliability of the capacitor after it is constructed.Another drawback is that the interconnections take up space within thecapacitor. This increases the size of the capacitor, which isundesirable when the capacitors are used for implantable medical devicessuch as defibrillators.

Thus, what is needed is a simple way to provide the anode and cathodeinterconnections of capacitors with as few steps as possible and whichlends itself to mass producing said capacitors.

SUMMARY

To address these and other needs, interconnection structures and methodsfor flat capacitors have been devised. In one embodiment, a methodincludes connecting together one or more anode connection members of oneor more anode foils and one or more cathode connection members of one ormore cathode foils and electrically isolating the one or more anodefoils from the one or more cathode foils. Among other advantages, themethod reduces the processing steps for interconnecting the foils of acapacitor, and provides a capacitor having a smaller amount of roomtaken up by its interconnections.

In one aspect, a capacitor having a first anode layer, a second anodelayer, a cathode layer between the first anode layer and the secondanode layer, a first separator layer between the first anode layer andthe cathode layer, a second separator layer between the second anodelayer and the cathode layer; and a conductive interconnect between thefirst anode layer and the second anode layer, the conductiveinterconnect passing through a cathode hole in the cathode; wherein theconductive interconnect has a cross section which is smaller than thecathode hole and the conductive interconnect is placed to avoid directelectrical contact with the cathode layer and wherein the first anodeand the second anode are electrically connected through the conductiveinterconnect.

Another aspect of the present invention includes various implantablemedical devices, such as pacemakers, defibrillators, and cardioverters,incorporating one or more capacitors having one or more of the novelfeatures described above.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an isometric view of a flat capacitor according to oneembodiment of the present invention.

FIG. 2A is a top view of an anode foil for use in constructing acapacitor according to one embodiment of the present invention.

FIG. 2B is a top view of a cathode foil for use in constructing acapacitor according to one embodiment of the present invention.

FIG. 3A is a top view of an anode foil for use in constructing acapacitor according to one embodiment of the present invention.

FIG. 3B is a top view of a cathode foil for use in constructing acapacitor according to one embodiment of the present invention.

FIG. 4 is a perspective view of a stack of one or more anodes andcathodes of FIGS. 2A and 2B.

FIG. 5 is a perspective view of the stack of FIG. 4 after the stack hasbeen processed according to one embodiment of the present invention.

FIG. 6 is a flowchart depicting a method of interconnecting anodes andcathode foils of a capacitor according to one embodiment of the presentinvention.

FIG. 7 shows a top view of a capacitor stack according to oneembodiment.

FIG. 8 shows a cross-section of a portion of FIG. 7.

FIG. 9 shows a partially etched anode foil according to one embodiment.

FIG. 10 shows a side view of a foil having masks according to oneembodiment.

FIG. 11 show a top view of FIG. 10.

FIG. 12 shows a method according to one embodiment.

FIG. 13 is a block diagram of a generic implantable medical deviceincluding a capacitor according to one embodiment of the presentinvention.

DETAILED DESCRIPTION

The following detailed description, which references and incorporatesthe figures, describes and illustrates one or more specific embodimentsof the invention. These embodiments, offered not to limit but only toexemplify and teach the invention, are shown and described in sufficientdetail to enable those skilled in the art to practice the invention.Thus, where appropriate to avoid obscuring the invention, thedescription may omit certain information known to those of skill in theart.

FIG. 1 shows a flat capacitor 100 constructed according to oneembodiment of the present invention. Although capacitor 100 is aD-shaped capacitor, in other embodiments, the capacitor is anotherdesirable shape, including, but not limited to rectangular, circular,oval or other symmetrical or asymmetrical shape. Capacitor 100 includesa case 101 which contains a capacitor stack 102. In the exemplaryembodiment, case 101 is manufactured from a conductive material, such asaluminum. In other embodiments, the case is manufactured using anonconductive material, such as a ceramic or a plastic.

Capacitor 100 includes a first terminal 103 and a second terminal 104for connecting capacitor stack 102 to an outside electrical component,such as heart monitor circuitry, including defibrillator, cardioverter,and pacemaker circuitry. In the exemplary embodiment, terminal 103 is afeedthrough terminal insulated from case 101, while terminal 104 isdirectly connected to case 101. In other embodiments, the capacitorincorporates other connection methods, depending on other designfactors. For instance, in some embodiments, capacitor 100 includes twoor more feedthrough terminals 103.

Capacitor stack 102 includes capacitor elements 105 a, 105 b, 105 c, . .. , 105 n, with each capacitor element 105 a–105 n including one or morecathodes, anodes, and separators. Each cathode is a foil structure andcan include aluminum, tantalum, hafnium, niobium, titanium, zirconium,and combinations of these metals. In one embodiment, each cathode ofcapacitor stack 102 is connected to the other cathodes by welding orother connection methods which will be discussed below. The cathodes arecoupled to conductive case 101, and terminal 104 is attached to case 101to provide a cathode connection to outside circuitry. In someembodiments, the cathode is coupled to a feedthrough conductor extendingthrough a feedthrough hole.

The separator is located between each anode and cathode. In oneembodiment, the separator includes one or more sheets of kraft paperimpregnated with an electrolyte. In one embodiment, the separatorincludes two sheets of paper. The electrolyte can be any suitableelectrolyte for an electrolytic capacitor, such as an ethylene-glycolbase combined with polyphosphates, ammonium pentaborate, and/or anadipic acid solute.

In one embodiment, one or more of the anodes of capacitor stack 102 is amulti-anode stack which includes three foil layers. In otherembodiments, one or more anode stacks include one, two, three or moreanode foils having a variety of anode shapes. The anode foils aregenerally foil structures and can include aluminum, tantalum, hafnium,niobium, titanium, zirconium, and combinations of these metals. In oneembodiment, at least portions of a major surface of each anode foil isroughened or etched to increase its effective surface area. Thisincreases the capacitive effect of the foil with no relative increase involume. Other embodiments incorporate other foil compositions and/orclasses of foil compositions.

In one embodiment, each anode is connected to the other anodes of thecapacitor and coupled to feedthrough assembly 103 for electricallyconnecting the anode to circuitry outside the case. In some embodiments,the anodes are connected to the case and the cathodes are coupled to afeedthrough assembly. In other embodiments, both the anode and thecathode are connected to feedthroughs.

FIG. 2A shows an anode 202 according to one embodiment of the presentinvention. Anode 202 is shown before it is assembled into capacitorstack 102 as shown in FIG. 1. Anode 202 includes a main body portion 204having one or more connection members 206. In one embodiment, connectionmember 206 includes one or more separate members attached to the anodeby welding, staking, or other connection method.

In other embodiments, connection member 206 is an integral portion ofanode 202, and is punched, laser-cut, or otherwise shaped from the anodefoil. In such an embodiment, portions of connection member 206 are notetched along with the rest of anode 202. For instance, a chemical maskis put on portions of connection member 206 to keep those maskedportions from becoming etched during the etching process. As will bediscussed below, this provides that those unetched, non-porous sectionsmake welding the edges of the anodes to each other easier.

Connection member 206 includes a proximal section 208 and distal section210. In the embodiment of FIG. 2A, connection member 206 is an L-shapedmember. However, it can also be hook shaped, U-shaped, and/or have othershape. In one embodiment, a portion of a distal section 210 along itsouter edge is unetched, as discussed above.

In one embodiment, proximal section 208 is connected to main body 204and is defined in part by a pair of cut-out portions 212 and 214 locatedon opposing sides of proximal section 208. Distal section 210 isconnected to a portion of proximal section 208. In one embodiment, it isintegral with proximal section 208. In some embodiments, distal section210 is attached as a separate member. In one embodiment, distal section210 is defined in part by a cut-out portion 216 which is located betweenmain body 204 and distal section 210, and a cut-out portion 218 whichseparates distal section 210 from main body 204.

In this embodiment, connection member 206 is located within the generalperimeter or outline of anode 202. In other embodiments, connectionmember extends further from the main body of anode 202 or connectionmember 206 is more internal within the main body of anode 202.

In some embodiments, each anode foil in capacitor stack 102 includes aconnection member such as connection member 206. In other embodiments,one or more anode foils in a multi-anode stack have a connection member206 while the other anode foils in the multi-anode stack are connectedto the anode having the connection member. For instance, in oneembodiment, a three-foil anode stack includes one foil having anconnection member 206 and two foils without connection members. The twofoils without connection members are welded, staked, or otherwiseattached to the foil having the connection member.

FIG. 2B shows a cathode 302 according to one embodiment of the presentinvention. Cathode 302 is shown before it is assembled into capacitorstack 102 as shown in FIG. 1. Cathode 302 includes a main body portion304 having one or more connection members 306. In one embodiment,connection member 306 is an integral portion of cathode 302, and ispunched, laser-cut, or otherwise shaped from the anode foil. In oneembodiment, connection member 306 includes one or more separate membersattached to the anode by welding, staking, or other connection method.

In one embodiment, connection member 306 includes a proximal section 308and a distal section 310. In the embodiment of FIG. 2B, connectionmember 306 is an L-shaped member. However, in some embodiments it ishook shaped, U-shaped, and/or have other shape.

In one embodiment, proximal section 308 is connected to main body 304and is defined in part by a pair of cut-out portions 312 and 314 locatedon opposing sides of proximal section 308. Distal section 310 isconnected to a portion of proximal section 308. In one embodiment, it isintegral with proximal section 308. In some embodiments, distal section310 is attached as a separate member. In one embodiment, distal section310 is defined in part by a cut-out portion 316 which is located betweenmain body 304 and distal section 310, and a cut-out portion 318 whichseparates distal section 310 from main body 304.

In this embodiment, connection member 306 is located within the generalperimeter or outline of cathode 302. In other embodiments, connectionmember 306 extends further from the main body of cathode 302 orconnection member 306 is more internal within the main body of cathode302.

FIGS. 3A and 3B show an anode 202′ and a cathode 302′ according to oneembodiment of the present invention. Anode 202′ and cathode 302′ areshown before it is assembled into capacitor stack 102 as shown inFIG. 1. Anode 202′ and cathode 302′ are generally similar to anode 202and cathode 302, respectively, except connection member 206′ does notinclude a cut-out such as cut-out 212 of anode 202 and connection member306′ does not include a cut-out such as cut-out 318 of cathode 302.Other embodiments utilize other shapes and locations for connectionmembers such as connection members 206, 206′, 306, and 306′,

For instance, in various embodiments, connection members 206 and 306 maybe in different positions along the edges or even within the main bodyportions of the capacitor foils 202 and 302. For instance, in someembodiments connection members 206 and 306 are located along edges 220and 320 of the respective foils 202 and 302. In some embodiments, theportions are located along curved edges 222 and 322 of the respectivefoils 202 and 302. In other embodiments, the portions may be cut-outwithin main bodies 204 and 304.

In one embodiment, proximal section 308 of cathode 302 and proximalsection 208 of anode 202 are located in different positions (relative toeach other) on their respective foils, while distal sections 210 and 310are generally commonly positioned. For instance, in one embodimentconnection members 206 and 306 of the anode 202 and the cathode 302,respectively, are mirror images of each other. In some embodiments,connection members 206 and 306 have generally reverse images of eachother.

FIG. 4 shows a stack 402 of one or more alternating anodes 202 andcathodes 302. As shown in FIG. 4, connection members 206 and 306 areoverlaying and underlying each other. As used herein, overlay andunderlay refer to the position or location of portions of the foilswhich are commonly positioned from a top view. In the embodiment of FIG.4, it is seen that connection members 206 and 306 have some commonlypositioned portions relative to each other and some portions which areexclusively positioned relative to each other.

For instance, proximal sections 208 of anodes 202 are exclusivelypositioned or located. This means that at least a portion of proximalsections 208 do not overlay or underlay a portion of cathodes 302.Likewise, proximal sections 308 of cathodes 302 are exclusive portionsand include at least a portion not overlaying or underlaying a portionof anode 202. Conversely, distal sections 210 and 310 are commonlypositioned and each include at least a portion overlaying or underlayingeach another. Cut-out portions 214 and 314 are also commonly positioned.Cut-out 218 is commonly positioned with cut-out 312 while cut-out 212 iscommonly positioned with cut-out 318.

When stacked as shown in FIG. 4, the edges of distal sections 210 and310 form a surface 410. In this embodiment, surface 410 can generally bedescribed as having a first portion 410 a which fronts the proximalsections 208 of anodes 202, a second portion 410 b which fronts commoncut-portions 214 and 314, and third portion 410 c which fronts theproximal sections 308 of cathodes 302.

In this embodiment, distal sections 210 and 310 of anode connectionmember 206 and cathode connection member 306 are fully overlaying oneanother. Fully overlaying means that there are generally no gaps alongsurface 410 of stack 402 when the anodes and cathodes are stacked as inFIG. 4. The fully overlayed structure of stack 402 provides a completesurface 410 which provides for ease of edge-welding or otherwiseconnecting connection members 206 and 306 together, as will be describedbelow. Other embodiments leave one or more gaps in surface 410 when theanodes and cathodes are stacked. For instance, in some embodiments, oneor more of distal sections 210 or 310 may not reach all the way acrossfront surface 410.

After being stacked as discussed above, at least portions of connectionmembers 206 and 306 are connected to each other. For instance, in oneembodiment portions of distal sections 210 and 310 are connected to eachother. In one embodiment, distal sections 210 and 310 are edge-weldedall along surface 410. In one embodiment, distal sections 210 and 310are only connected along portion 410 a and 410 c of surface 410. In oneembodiment, distal sections 210 and 310 are soldered along surface 410.In some embodiments, portions of distal sections 310 and 210 are staked,swaged, laser-welded, or connected by an electrically conductiveadhesive. In other embodiments, portions of proximal sections 208 areconnected to each other and/or portions of proximal sections 308 areconnected to each other.

After being connected, portions of connection members 206 and 306 areremoved or separated so that proximal sections 208 and 308 areelectrically isolated from each other. As used herein, electricallyisolated means that sections 208 and 308 are electrically insulated fromeach other at least up to a surge voltage of capacitor 100.

FIG. 5 shows stack 402 after portions of distal sections 210 and 310have been removed from the stack, forming a separation 502 between anodeconnection members 206, which together comprise anode connection section508, and cathode connection members 306, which together comprise cathodeconnection section 510. Separation 502 in the present embodimentelectrically isolates section 508 from section 510. Proximal sections308 are still coupled to each other as are proximal sections 208. Insome embodiments, separation 502 is a thin slice. In some embodiments,separation 502 is as wide as cut-outs 214 and 314, as shown in FIG. 5.In some embodiments, an electrically insulative material is inserted inseparation 502. In various embodiments, separation 502 is formed bylaser cutting, punching, and/or tool or machine cutting.

FIG. 6 shows a flowchart depicting a method 600 for interconnecting twoor more foils of a capacitor according to one embodiment of the presentinvention. Method 600 includes a block 602, positioning the connectionmembers of two or more foils, a block 604, connecting the connectionmembers, and block 606, electrically isolating portions of theconnection members from each other.

In one embodiment, block 602, positioning the connection members of twoor more foils, includes stacking an anode foil having a connectionmember having a proximal section and a distal section upon a cathodefoil having a connection member having a proximal section and a distalsection. The foils and connection members are positioned so that theproximal section of the anode foil connection member does not overlaythe proximal section of the cathode foil connection member and thedistal section of the anode foil connection member at least partiallyoverlays the distal section of the cathode foil connection member.

In one embodiment, block 604, connecting the connection members,includes connecting the connection member of the anode foil to theconnection member of the cathode foil. In one embodiment, this includesconnecting the distal section of the anode connection member and thedistal section of the cathode connection member at a portion of theanode connection member that overlays (or underlays) the portion of thecathode connection member. In one embodiment, connecting comprises asingle, continuous connection process. For instance, a laser weld orstaking process is performed which attaches all the anode and cathodefoil connection members together during a single, uninterrupted process.In one embodiment, the connection is performed by edge-welding at leasta portion of the distal sections of the anode foil and the cathode foiltogether. One embodiment includes a laser edge-welding process.

Alternatively, in some embodiments, a portion of the stack is weldedduring a different process or by a different method than the firstprocess. Some embodiments include soldering, staking, swaging, and/orapplying an electrically conductive adhesive.

In one embodiment, connection members 206 and 306 are laser edge-weldedto each other by a process as discussed in co-pending U.S. patentapplication Ser. No. 09/706,518, filed on Nov. 3, 2000, thespecification of which is incorporated herein by reference.

In one embodiment, block 606, electrically isolating portions of theconnection members from each other, includes removing portions of theanode connection member and the cathode connection member. In oneembodiment, the removed portion includes where the cathode connectionmember overlays (or underlays) a portion of the anode connection member.In one embodiment, this includes removing a portion of the distalsections of the anode connection member and the cathode connectionmember. In one embodiment, electrically isolating comprises punching-outa portion of the distal section of the anode foil connection member andthe distal section of the cathode foil connection member. In oneembodiment, electrically isolating includes laser cutting a portion ofthe distal section of the anode connection member and the distal sectionof the cathode connection member.

After being processed as discussed above in block 606, proximal sections208 of the connection members of anodes 202 are still coupled togetherand proximal sections 308 of the connection members of cathodes 302 arestill coupled to each other, while the anodes 202 and cathodes 302 areelectrically isolated from each other. Feedthroughs or other terminalmembers are then used to couple the anodes and cathodes to outsidecircuitry.

One aspect of the present capacitor includes a system forinterconnecting anode layers in a flat capacitor stack using vias. Inone embodiment, vias are employed to interconnect anode layers. In oneembodiment, the vias are made by inserting conductive interconnectswhich interconnect anode layers without contacting an interveningcathode layer.

For example, FIG. 7 shows a top view of a cathode and anode layerseparated by separator (for example, kraft paper). The cathode layerincludes one or more holes which provide ample clearance for aconductive interconnect. The x-section of FIG. 7, shown in FIG. 8, showsthat the conductive interconnect will interconnect anode layers withoutcontacting an intervening cathode layer. Thus, the cross section of thecathode hole exceeds that of the conductive interconnect to avoidshorting the cathode to the anodes. The conductive interconnect iselectrically connected to the anodes by welding, such as ultrasonic,resistance or other types of welding.

One way to facilitate connections is to use a masking process forconnection surfaces on the foil to ensure that the masked surfaces arenot etched and/or formed. One way to avoid mechanical breakage of thefoils is to use a masking technique which provides gradually non-etchedportions of the foil to avoid mechanical stresses (e.g. high stresspoints) due to discontinuites of etching and which provides a suitableregion for interconnection of the via to the foil. This is demonstratedby FIG. 9. The vertical lines show the cross-section of unmasked andmasked foil portions. The figure shows that foil etching graduallydiminishes over the transition from masked portion to unmasked portion.It is noted that the example shows a pure aluminum foil, but that otheretchings and foils may be masked without departing from the scope of thepresent system.

FIG. 10 shows a side view of a foil and positions of the masks for oneembodiment of the present system. The top view is provided in FIG. 11.The positions, shapes and sizes of the masks may vary without departingfrom the present system, and the demonstrated masks are shown toillustrate the system and are not intended in an exhaustive or exclusivesense. In one embodiment, thickness t is 100 micrometers. However, it iscontemplated that other thicknesses may be used without departing fromthe present system. For example, other thicknesses, including, but notlimited to, 50–600 micrometers may be used.

The foil dimensions are shown as 500×250 millimeters, but other sizedfoils may be employed without departing from the scope of the presentsystem. In one application of the present system, a master roll of foilis masked to provide d-shaped cutouts with accurately placed masks wherethe conductive interconnects are to contact the foil. In oneapplication, the spacing between foils must be large enough to provide a“web” for processing the cutouts.

FIG. 12 shows one process for providing one embodiment of a capacitoraccording to some of the teachings herein. Raw foil is masked byprinting the mask on the foil. The masked foil is etched and then themask is removed. Oxides are formed on the foil and it is then cut intosubrolls. The subrolls are processed by cutting shapes for the finalcapacitor out of the subrolls. The foil shapes are used to make thecapacitors.

The cathode foils are processed to accurately place the cathode holes,which correspond to anode mask layers when overlapped. Paper separatorsare also cut to provide space for the conductive interconnects. In oneapplication, the perimeter of the paper is smaller than that of thecathode to provide a nonconductive guide for the conductiveinterconnect. In alternate embodiments, an insulator may be used toposition the conductive interconnect and to insulate against cathodecontact.

It is noted that the conductive interconnects may be connected to formedor unformed portions of the anode layer.

One way to manufacture a capacitor according to the present teachings isto use a robotic assembly method, whereby anodes which are alreadymasked, etched, and formed are stacked, followed by separator material,and then cathode material. In one assembly process, the cathodes areprecision punched to provide accurately placed cathode holes. The robotcan use the cathode features to accurately place the cathode relative tothe anodes. A separator layer and an anode layer are also placed overthe cathode using the robot. In embodiments where the conductiveinterconnect is a metal plug, the robot places the conductive plugaccurately prior to the placement of the separator and anode layers.This process may be repeated to provide a stack of anodes of multiplelayers interspersed with separator and cathode layers. The robot canalso be used to perform the welding steps.

Other types of conductive interconnects may be used without departingfrom the present system. For example, the conductive interconnects maybe made of a non-circular cross section. The conductive interconnectsmay be made of a suitable metal, such as aluminum. The conductiveinterconnects may also be made of other materials, including, but notlimited to, conductive epoxy, conductive polymer (such as polyimidefilled with aluminum), or fused aluminum powder. The metal used in theconductive interconnect should match the anode metal. Other anodemetals/interconnect metal pairs may be used including, but not limitedto, tantalum, hafnium, niobium, titanium, zirconium, or combinations ofthese metals.

It is understood that other connections may be performed using theteachings provided herein. For example, it is possible to create aseries of interconnections between cathode layers using the teachingsprovided. Thus, use of the present system is not limited to anode-anodeconnections.

In one embodiment, the anode layers consist of a plurality of anodefoils. In one application it is possible that a single anode foil isinterconnected to a triple anode foil or any multiplicity of anode foilcombinations.

In one embodiment an anode layer may include a plurality of parts and/orlayers. For example, the anode layer may include two different anodeshapes in the same layer to provide a contoured edge. The shapes may beelectrically connected to provide an equipotential surface. The use ofmultiple anode parts for a single layer facilitates the construction ofa capacitor of virtually any form factor.

Furthermore, it is possible to weld multiple anode-cathode-anode stacksat different points for different conductive interconnects in oneoperation. Additionally, depending on the welding process used, severalanode/cathode layers can be welded in a single operation.

Some of the benefits of the present system include, but are not limitedto, the following: the electrical connection system provides mechanicalstability; and alignment to the stack as the layers are being assembled;taping is not required; the assembly is ready for insertion into thecapacitor case; surface area is optimized; interior alignment isfacilitated using interior features to align the stack layer to layer;edge-welding and/or intra-anode staking may be eliminated; and, in someembodiments, paper gluing may be eliminated.

EXEMPLARY EMBODIMENT OF IMPLANTABLE DEFIBRILLATOR

FIG. 13 shows one of the many applications for capacitors incorporatingone or more teachings of the present invention: an implantable heartmonitor or apparatus 700. As used herein, implantable heart monitorincludes any implantable device for providing therapeutic stimulus to aheart muscle. Thus, for example, the term includes pacemakers,defibrillators, cardioverters, congestive heart failure devices, andcombinations and permutations thereof.

Heart monitor 700 includes a lead system 703, which after implantationelectrically contact strategic portions of a patient's heart. Shownschematically are portions of monitor 700 including a monitoring circuit702 for monitoring heart activity through one or more of the leads oflead system 703, and a therapy circuit 701 for delivering electricalenergy through one or more of the leads to a heart. Monitor 700 alsoincludes an energy storage component, which includes a battery 704 andincorporates at least one capacitor 705 having one or more of thefeatures of the exemplary capacitors described above.

In addition to implantable heart monitor and other cardiac rhythmmanagement devices, one or more teachings of the present invention canbe incorporated into cylindrical capacitors and/or capacitors used forphotographic flash equipment. Indeed, teachings of the invention arepertinent to any application where high-energy, high-voltage, orspace-efficient capacitors are desirable. Moreover, one or moreteachings are applicable to batteries.

CONCLUSION

In furtherance of the art, the inventors have devised connectionstructures and methods for interconnecting the anode foils and thecathode foils of capacitors. In one embodiment, a method includesconnecting together one or more anode connection members of one or moreanode foils and one or more cathode connection members of one or morecathode foils and electrically isolating the one or more anode foilsfrom the one or more cathode foils. Among other advantages, theexemplary method reduces the number of processing steps for constructinga capacitor.

It is understood that the above description is intended to beillustrative, and not restrictive. Many other embodiments will beapparent to those of skill in the art upon reviewing the abovedescription. The scope of the invention should, therefore, be determinedwith reference to the appended claims, along with the full scope ofequivalents to which such claims are entitled.

1. Foil structures for use in constructing a capacitor, the foilstructures comprising: an anode foil having a connection portioncomprising a proximal section and a distal section; and a cathode foilhaving a connection portion comprising a proximal section and a distalsection; wherein the proximal section of the anode foil does not overlaythe proximal section of the cathode foil and the distal section of theanode foil at least partially overlays the distal section of the cathodefoil when the anode foil and the cathode foil are stacked together. 2.The foil structures of claim 1, wherein the connection portion of theanode foil comprises an L-shaped member.
 3. The foil structure of claim2, wherein the connection portion of the cathode foil comprises anL-shaped member, the cathode L-shaped member having a generally reverseimage relative to the anode L-shaped member when the anode foil and thecathode foil are stacked together.
 4. The foil structure of claim 1,wherein the anode connection member includes at least a partiallyunetched portion.
 5. The foil structures of claim 1, wherein the anodefoil and cathode foil are substantially flat.
 6. The foil structures ofclaim 1, wherein the anode foil includes aluminum.
 7. The foilstructures of claim 1, wherein the anode foil is at least partiallyetched.
 8. The foil structures of claim 1 wherein the cathode foilincludes aluminum.
 9. A foil stack, comprising: a plurality of anodefoils, each anode foil includes an anode connection member having adistal section and a proximal section; a plurality of cathode foils,each cathode foil includes a cathode connection member having a distalsection and a proximal section; and a separator between each anode foiland cathode foil; wherein the anode foils and cathode foils are stackedtogether such that the distal section of the anode connection membersoverlay the distal section of the cathode connection members.
 10. Thefoil stack of claim 9, wherein the connection members of the anode foilsare connected to the connection members of the cathode foils.
 11. Thefoil stack of claim 9, wherein the anode connection members and thecathode connection members are stacked such that the proximal section ofthe anode connection members do not overlay the proximal section of thecathode connection members.
 12. The foil stack of claim 9, theconnection members of the anode foils are connected to the connectionmembers of the cathode foils by a weld.
 13. The foil stack of claim 9,wherein the anode connection members include at least a partiallyunetched portion.
 14. The foil stack of claim 9, wherein the anode foilsand cathode foils are substantially flat.
 15. The foil structures ofclaim 9, wherein the anode foils include aluminum foils.
 16. The foilstructures of claim 9, wherein the anode foils are at least partiallyetched.
 17. The foil structures of claim 9, wherein the cathode foilsinclude aluminum foils.
 18. The foil structures of claim 9, wherein theconnection members of the anode foils include an L-shape.
 19. The foilstructures of claim 9, wherein the connection members of the cathodefoils include an L-shape.